The present proposal is designed to elaborate, test, and refine predictions from a theory of memory development based on data from the research on long-term memory in motivated human infants, on animal learning, and on human adult memory. "Memory development" refers both to changes in a given memory over time and to age-related changes in memory processing. Both will be studied. The proposed research will address (1) temporal factors involved in the definition of the unit of analysis (an "event") at different ages, including the temporal integration of distinctive events; (2) the relative accessibility of memory attributes and changes in accessibility during forgetting and retrieval for infants of different ages; (3) memory malleability and maintenance over successive retrievals; (4) the role of context and the gating function of context in modulating retention; (5) memories for response rules; and (6) age-related changes in retrieval cue utilization. All studies will be with motivated infants between 2 and 12 months of age who will be trained in an age-appropriate conjugate reinforcement task and tested for retention after appropriate intervals during nonreinforcement. Both simple forgetting and memory reactivation paradigms will be used. This research will provide a systematic analysis of the basic learning and memory processes during early development and will provide new data which illumine the basic processes of human adult memory. By drawing on research and theory from animal learning and human memory, we seek to provide a comparative basis for understanding the correspondences between these two disparate traditions. By providing a detailed analysis of human memory during the first postnatal year, we seek to describe the course of early cognitive development and the factors that contribute to it. In this way, the proposed research should provide a better understanding of such basic cognitive processes as how infants categorize information, how their memories are organized and modified, and how early experiences contribute to cognitive development over the short and long term. Finally, the proposed research should provide (1) a solid core of developmental data which can be used as the basis for specifying the nature of early cognitive deficits and a set of techniques and (2) a set of well-defined procedures which could be adapted to screen for early cognitive risk.